Keyboard instrument

ABSTRACT

In a predetermined sound generation mode, a drive signal having a frequency characteristic corresponding to an operated key is supplied to excitation units provided on a soundboard. The soundboard is vibrated in response to a mechanical vibration generated by the excitation units to generate an acoustic sound by the vibration of the soundboard. The frequency characteristics of the drive signal to be supplied to each of the excitation units is set in association with the vibration characteristics of the soundboard at a position of a vibration member of each excitation unit connected to the soundboard. For example, the frequency characteristics of the drive signal is set to characteristics capable of suppressing resonance of the soundboard.

BACKGROUND

The present invention relates to a technology for enriching a sound(i.e., musical sound or tone) of an acoustic keyboard instrument.

Usually, an electronic piano has no soundboard unlike an acoustic piano,because the electronic piano is configured to produce electronic soundfrom a speaker. However, Japanese patent application laid-openpublication No. JP2008-292739A discloses a technology of mounting asoundboard on the electronic piano and installing speakers on thesoundboard so that by exciting the soundboard with the speakers, avibration sound is radiated from the soundboard. As a result, theelectronic piano can produce not only electronic sounds but alsoenriched acoustic low-pitched sounds due to radiation of the vibrationsounds from the soundboard. The above-mentioned patent literature alsodiscloses that such a technology can be applied to not only theelectronic piano but also a case where the acoustic piano is configurednot to vibrate any strings (sound-deadening piano).

The sound quality of the acoustic piano largely depends on the vibrationcharacteristics of the soundboard which radiates sounds. When thesoundboard is excited with a speaker mounted on the soundboard of theacoustic piano, the soundboard may sometimes resonate at specificfrequency bands depending on a mounting position thereof. In this case,a sound quality of a vibration sound from the speaker may be changed dueto an influence of resonance characteristics or a string correspondingto its resonance frequency may be vibrated so that an unexpected soundmay be sometimes generated.

Thus, it is necessary to consider the mounting position carefully, mounta speaker at a position which never induce any resonance and adjust thevibration characteristics by changing a design of the soundboard. Whenthe number of speakers to be mounted is increased, it may be difficultto select the mounting positions and design the soundboard properly.

SUMMARY OF THE INVENTION

In view of the foregoing prior art problems, an object of the presentinvention is to provide a keyboard instrument capable of generating anacoustic sound by vibrating the soundboard and controlling an influenceof vibration characteristics of the soundboard on the sound quality ofthe sound generated based on the vibration of the soundboard.

In order to accomplish the above-mentioned object, the present inventionprovides an improved keyboard instrument which comprises: a plurality ofkeys (2); a plurality of sounding bodies (5) each provided incorresponding relation to each of the plurality of keys (2); a pluralityof hammers (4) each responsive to an operation of any one of the keysand adapted to strike the sounding body (5) corresponding to theoperated key; a soundboard (7) configured to be vibrated with vibrationof the sounding body; an excitation unit (50) comprising a vibrationmember (51; 81) connected to a given position on the soundboard (7) andadapted to vibrate the soundboard (7) via the vibration member (51; 81)in response to a drive signal supplied thereto; a performanceinformation generation unit (120) adapted to generate performanceinformation corresponding to an operation of the key; and a signalgeneration unit (15) adapted to generate an audio waveform signal basedon the performance information, the generated audio waveform signalbeing supplied to the excitation unit (50) as the drive signal tovibrate the vibration member (51, 81), wherein the signal generationunit (15) generates the audio waveform signal having frequencycharacteristics which are adjusted in association with vibrationcharacteristics of the soundboard (7) at the given position where thevibration member (51; 81) is connected to. Note that the same referencecharacters as used for various constituent elements of later-describedembodiments of the present invention are indicated in parentheses herefor ease of understanding.

With this arrangement, because the signal generation unit (15) generatesthe audio waveform signal having frequency characteristics which areadjusted in association with the vibration characteristics of thesoundboard (7) at the given position where the vibration member (51; 81)is connected to, it is capable of easily controlling an influence ofvibration characteristics of the soundboard on the sound quality of thesound generated based on the vibration of the soundboard.

According to a preferred embodiment of the present invention, aplurality of the excitation units (50) are provided on different givenpositions of the soundboard (7), wherein the signal generation unit (15)generates a plurality of the audio waveform signals each having thefrequency characteristics unique to each excitation unit (50).

According to another embodiment of the present invention, the signalgeneration unit (15) generates the audio waveform signal having thefrequency characteristics for suppressing resonance characteristics ofthe soundboard at the given position where the corresponding vibrationmember (51; 81) is connected to.

According to still another embodiment of the present invention, thesignal generation unit (15) generates the audio waveform signal havingthe frequency characteristics corresponding to substantially inversecharacteristics to the vibration characteristics of the soundboard atthe given position where the corresponding vibration member (51; 81) isconnected to.

According to a further embodiment of the present invention, a firstbridge (6L) and a second bridge (6H) are provided on the soundboard (7),and the excitation unit includes a first excitation unit (50L) connectedto a position corresponding to the first bridge on the soundboard and asecond excitation unit (50H) connected to a position corresponding tothe second bridge on the soundboard.

According to a further embodiment of the present invention, any one of aplurality of sound generation modes is selectable, and when apredetermined special sound generation mode is selected by a user fromamong the plurality of the sound generation modes, the soundboard isvibrated by the excitation unit (50).

According to a still further embodiment of the present invention, theexcitation unit (50) includes a voice coil (511) adapted to be driven bythe drive signal, and the keyboard instrument further comprises afrequency characteristic setting unit (160, 155) adapted to, in order topreviously set up the frequency characteristics, cause a vibration inthe soundboard (7); measure a voltage induced in the voice coil inresponse to the vibration caused in the soundboard (7); specify thevibration characteristics of the soundboard based on the measuredvoltage; and set up the frequency characteristics of the audio waveformsignal to be generated by the signal generation unit (15) based on thespecified vibration characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain preferred embodiments of the present invention will hereinafterbe described in detail, by way of example only, with reference to theaccompanying drawings, in which:

FIG. 1 is a perspective view showing an outer appearance of a grandpiano according to an embodiment of the present invention;

FIG. 2 is a view explanatory of an internal construction of the grandpiano according to the embodiment;

FIG. 3 is a view explanatory of an arrangement of an excitation unit inthe grand piano according to the embodiment;

FIG. 4 is a perspective view showing an outer appearance of theexcitation unit according to the embodiment;

FIG. 5 is a cross-sectional view of the excitation unit shown in FIG. 4.

FIG. 6 is a cross-sectional view explanatory of a structure of a voicecoil included in the excitation unit according to the embodiment;

FIGS. 7A to 7C are cross-sectional views showing three different typesof voice coils to illustrate an optimum construction the voice coil tobe used in the excitation unit according to the embodiment;

FIGS. 8A to 8C are cross-sectional views showing three differentarrangements of yokes to illustrate an optimum arrangement of a yoke inthe excitation unit according to the embodiment;

FIG. 9 is a block diagram showing a construction of a controller in thegrand piano according to the embodiment;

FIG. 10 is a block diagram showing a functional construction of thegrand piano according to the embodiment;

FIG. 11 is a block diagram showing a modification of the functionalconstruction shown in FIG. 10;

FIGS. 12A and 12B are graphs illustrating an adjustment of frequencycharacteristics to be set in an equalizer unit in the grand pianoaccording to the embodiment;

FIG. 13 is a diagram showing a mechanism in which a frequencycharacteristics specifying section unit specifies the frequencycharacteristics to be set in the equalizer unit;

FIG. 14 is a cross-sectional view explanatory of the excitation unitaccording to modification 1 of the present invention;

FIG. 15 is a view explanatory of an internal construction of an uprightpiano according to modification 2 of the present invention;

FIG. 16 is a view explanatory of an arrangement of the excitation unitin the upright piano according to modification 2;

FIG. 17 is a side view showing a state in which the excitation unit ismounted onto a soundboard according to modification 3 of the presentinvention;

FIG. 18 is a view explanatory of an arrangement of the excitation unitaccording to modification 7 of the present invention;

FIG. 19 is a view explanatory of an internal construction of the uprightpiano according to modification 7 of the present invention;

FIG. 20 is a cross-sectional view explanatory of an excitation unitaccording to modification 9 of the present invention;

FIG. 21 is a cross-sectional view explanatory of an excitation unitaccording to modification 12 of the present invention; and

FIGS. 22A and 22B are cross-sectional views explanatory of an excitationunit according to modification 13 of the present invention.

DETAILED DESCRIPTION Overall Configuration

FIG. 1 is a perspective view showing an outer appearance of a grandpiano 1 according to an embodiment of the present invention. Like knowngrand pianos, the grand piano 1 has a keyboard in which a plurality ofkeys 2 to be operated by a performer or user are arranged on its frontside and pedals 3 for controlling a musical performance. The grand piano1 also includes a control device 10 having an operation panel 13 on itsfront surface portion and a touch panel 60 provided on a portion of amusic stand. User's instructions can be input to the control device 10by user's operation of the operation panel 13 and the touch panel 60.

The grand piano 1 is configured to be capable of generating a sound in asound generation mode which is selected from among a plurality of soundgeneration modes in accordance with a performer's (user's) instruction.These sound generation modes include (1) normal sound generation mode,(2) sound damping mode, and (3) sound intensifying mode.

The normal sound generation mode (1) is a mode for generating a soundbased on only a vibration of a string generated in response to strikingof the string by a hammer corresponding to an operated key. The sounddamping mode (2), namely a “special sound generation mode 1”, is a modefor generating a sound based on only an actively-vibrated-soundboardsound which is generated from a soundboard when the soundboard isphysically vibrated according to a drive signal based on an audiowaveform signal generated from a sound source, such as an electronicsound source, in correspondence with an operation of a key, whilehammering of the string is blocked by means of a stopper. In otherwords, in the sound damping mode (2), the stopper is permitted toprevent the hammer from striking the string corresponding to theoperated key. Thus, the generated actively-vibrated-soundboard sound hasa feature of an acoustic sound having natural feeling.

The sound intensifying mode (3), namely a “special sound generation mode2”, is a mode for generating a sound based on both of the vibration ofthe string and the actively-vibrated-soundboard sound. In other words,in the sound intensifying mode (3), the stopper is not permitted toprevent the hammer from striking the string corresponding to theoperated key. It should be noted that, in the sound intensifying mode(3), not only a total volume of the generated sound can be intensified,but also a tone color layer effect can be achieved, because a firstacoustic sound based on striking of the string by the hammer (namely,the sound based on the vibration of the string) having a piano intrinsictone color and a second acoustic sound (namely, theactively-vibrated-soundboard sound) having an arbitrary additional tonecolor obtained by vibrating forcedly the soundboard according to thedrive signal having the audio waveform of an arbitrary tone color(including a tone color similar to a piano tone color) are generated atthe same time. Therefore, the sound intensifying mode (3) also functionsas a performance mode capable of obtaining the tone color layer effect.

The sound generation mode may include other sound generation modes suchas sound deadening mode. When the sound deadening mode is selected,under the same configuration as the sound damping mode, an electronicmusical sound signal (audio waveform signal) generated from a soundsource is supplied to a headphone terminal without being used as asoundboard drive signal. Consequently, a performer can listen to thesound based on the electronic musical sound signal in private (withoutspreading the musical sound into external space).

Table 1 lists the sound generation modes as follow.

TABLE 1 Function of blocking hammering of strings Invalid (with Valid(without hammering of strings) hammering of strings) No vibration by anSoundboard characteristics The acoustic piano functions excitation unitof an acoustic piano do not as a sound-deadening piano influenced, andthe acoustic in which a performer listens piano can be played at an to aplayed sound through a intrinsic performance of the headphone withoutsounding piano. (normal sound outside generation mode) With vibration byan Capable of not only Resonance of the string is excitation unitintensifying the volume of valid so that natural resonant (tone color ofpiano) sound but also obtaining an effect can be obtained. effect suchas a (sound damping mode) honky-tonk-piano-like-effect by slightlydetuning the actively-vibrated-soundboard sound (sound intensifyingmode) With vibration by an Obtaining an effect in which Enjoying playingat other excitation unit (other a sound of acoustic piano tone than thepiano tone tone colors than piano) and a actively-vibrated- color whileobtaining a soundboard sound of a feeling of the natural tone colorhaving an affinity acoustic field of the piano for the acoustic pianosound soundboard and a resonant like strings tone color are effect ofthe string (sound integrated on the soundboard damping mode) (soundintensifying mode)

Also, the grand piano 1 is constructed to be able to operate in aperformance mode selected by a user from among a plurality ofperformance modes. The performance modes includes a normal performancemode in which the user (performer) plays the piano to produce sound, andan automatic performance mode in which keys are automatically driven toproduce automatically-performed sounds. To carry out the presentinvention, the grand piano 1 may be configured to be capable ofrealizing at least any one of the performance modes.

[Construction of Grand Piano 1]

FIG. 2 is a view explanatory of an internal construction of a grandpiano 1 according to the embodiment of the present invention. In FIG. 2,an inner construction corresponding to only one key 2 is shown with aninner construction corresponding to the other keys 2 omitted forsimplicity of illustration.

Underneath a back end portion (i.e., end portion remote from the user ofthe grand piano 1) of each of the keys 2 is provided a key drive unit 30for driving the key 2 by use of a solenoid. The key drive unit 30 drivesthe solenoid in accordance with a control signal given from the controldevice 10. More specifically, the key drive unit 30 drives the solenoidto raise a plunger so as to reproduce a similar state to when the userhas depressed the key 2, and lowers the plunger to reproduce a similarstate to when the user has released the key 2. Namely, a differencebetween the ordinary performance mode and the automatic performance modeis whether the key 2 is driven by a user's operation or by the key driveunit 30.

Hammers 4 are provided in corresponding relation to the keys 2. Thus,once any one of the keys 2 is depressed by the user, depressing force istransmitted to the corresponding hammer 4 via an action mechanism (notshown), so that the hammer 4 moves to strike the corresponding string 5.A damper 8 is brought out of or into contact with the string 5 inaccordance with a depressed amount of the key 2 and a pressed-downamount of a damper pedal of the pedals 3; hereinafter, the “pedal 3”will refer to the damper peal unless otherwise stated. When in contactwith the string 5, the damper 8 suppresses vibration of the string 5.

Generally, in the acoustic grand piano, as well known in the art, acombination of a plurality of strings (or at least one string) isprovided in association with each key. In this disclosure, the string 5corresponding to one key 2 actually comprises such a combination of oneor a plurality of strings. Namely, in this disclosure, a combination ofone or a plurality of strings provided in association with each key willbe referred to as simply as “string 5” for convenience of description.

In the above-mentioned sound damping mode, a stopper 40 prevents thehammer 4 from striking the string 5. Namely, when the sound generationmode is set in the sound damping mode, a hammer shank collides againstthe stopper 40 so that the hammer 4 is prevented from striking thestring 5. On the other hand, when the sound generation mode is set inthe normal sound generation mode or the sound intensifying mode, thestopper 40 moves to a position where it does not collide against thehammer shank.

Key sensors 22 are provided in corresponding relation to the keys 2 andunderneath the corresponding keys 2, and each of the key sensors 22outputs a detection signal corresponding to a behavior of the key 2 tothe control device 10. In the illustrated example, each of the keysensors 22 detects a depressed amount of the corresponding key 2 andoutputs, to the control device 10, a detection signal indicative of thedetected depressed amount (detected result). Instead of outputting thedetected depressed amount of the key 2 as a detection signal, the keysensor 22 may output a detection signal indicating that the key 2 haspassed a particular depressed position. Here, the particular depressedposition refers to any suitable position, preferably a plurality ofpositions, within a range from a rest position to an end position of thekey 2. Namely, the detection signal to be output from the key sensor 22may be any kind of signal as long as it allows the control device 10 torecognize behavior of the corresponding key 2.

Hammer sensors 24 are provided in corresponding relation to the hammers4, and each of the hammer sensors 24 outputs, to the control device 10,a detection signal representing behavior of the corresponding hammer 4.In the illustrated example, the hammer sensor 24 detects a moving speedof the hammer 4 immediately before striking the string 5, and outputs,to the control device 10, a detection signal indicative of the detectedmoving speed (detected result). Note that this detection signal need notnecessarily be indicative of the moving speed of the hammer 4 itself andmay be indicative of a moving speed of the hammer 4 calculated in thecontrol device 10 as another form of detection signal. For example, thedetection signal may be one indicating that the hammer shank has passedtwo predetermined positions during movement of the hammer 4, or oneindicative of a time length from a time point at which the hammer shankhas passed one of the two positions to a time point at which the hammershank has passed the other of the two positions. Namely, the detectionsignal to be output from the hammer sensor 24 may be any kind of signalas long as it allows the control device 10 to recognize behavior of thecorresponding hammer 4.

Pedal sensors 23 are provided in corresponding relation to the pedals 3,and each of the pedal sensors 23 outputs, to the control device 10, adetection signal representing behavior of the corresponding hammer 3. Inthe illustrated example, the pedal sensor 23 detects a pressed-downamount of the pedal 3 and outputs, to the control device 10, a detectionsignal indicative of the detected pressed-down amount (detected resultof the pedal 3). Alternatively, the pedal sensor 23 may output adetection signal indicating that the pedal 3 has passed a particularpress-down position, instead of outputting a detection signalcorresponding to a pressed-down amount of the pedal 3. Here, the“particular press-down position” is any suitable position within a rangefrom a rest position to an end position of the pedal 3, and theparticular press-down position is desirably set at a position to permitdiscrimination between the contacting state where the damper 8 and thestring 5 are in complete contact with each other and the non-contactingstate where the damper 8 and the string 5 are out of contact with eachother. It is further desirable that a plurality of such particularpress-down positions be set so as to permit detection of a half-pedalstate as well. Namely, the detection signal to be output from the pedalsensor 23 may be any kind of signal as long as it allows the controldevice 10 to recognize behavior of the pedal 3.

As long as the control device 10 is constructed in such a manner that,with the detection signals output from the key sensors 22, pedal sensors23 and hammer sensors 24, it can identify, for each individual key (keynumber) 2, a time point (string-striking time point) at which the hammer4 has struck the string 5 (i.e., key-on event time), striking velocityand a time point (vibration-suppressing time point) at which the damper8 has suppressed vibration of the string (key-off event time point),then each of the key sensors 22, pedal sensors 23 and hammer sensors 24may output detected results of behavior of the key 2, pedal 3 and hammer4 as other forms of detection signals than the aforementioned.

As conventionally known in the art, a soundboard 7 of the piano isbacked with a plurality of ribs (or bracing members) 75, and a bridge 6spanning between the strings 5 are fixed to a front surface of thesoundboard 7. Hereinafter, the bridge 6 may refer to a “first bar-likemember” and ribs 75 may refer to a “second bar-like member”. In playingthe piano in an ordinary manner, vibration of the string 5 struck by thehammer 4 is propagated (or transmitted) to the soundboard 7 through thebridge 6.

According to the present invention, an excitation unit 50 is mounted ona suitable portion of the soundboard 7. The excitation unit 50 has avibrating member 51 connected to the soundboard 7 and a yoke-holdingunit (i.e., a main body) 52. The yoke-holding unit (main body) 52 issupported by a supporting unit 55 connected to a straight supportingcolumn 9. In a specified sound generation mode (namely, theabove-mentioned sound damping mode or sound intensifying mode), theexcitation unit 50 is supplied with a drive signal from the controldevice 10. The vibration member 51 vibrates in response to electronicaudio waveforms represented by a supplied drive signal to therebyvibrate the soundboard 7. In this way, an acoustic vibration sound isgenerated from the soundboard 7. The bridge 6 is also vibrated alongwith the vibration of the soundboard 7 and thus the vibration of thesoundboard 7 is propagated (or transmitted) to the strings 5 through thebridge 6. In one embodiment as shown in FIG. 5, the vibration member 51includes yokes 521, 523 contained in the yoke-holding unit 52 and avoice coil 512 arranged to be positioned in a magnetic path formed by amagnet 522 of a ring shape, and the vibration member 51 is vibratedaccording to a drive signal input by the voice coil 512.

FIG. 3 is a diagram, illustrating an arrangement of the excitation unit50 according to the embodiment of the present invention. In theillustrated example, as the excitation unit 50, two excitation units50H, 50L are provided. If it is not especially necessary to distinguishbetween the excitation unit 50H and the excitation unit 50L, anexpression of just the excitation unit 50 will be used.

In the illustrated example, the excitation units 50H, 50L are mounted ona rear surface of the soundboard 7 between two ribs 75. Of the twobridges 6 (namely, long bridge 6H and short bridge 6L), the excitationunit 50H is arranged at a position corresponding to the long bridge 6H,and the excitation unit 50L is arranged at a position corresponding tothe short bridge 6L. That is, it comes that the soundboard 7 issandwiched by the excitation units 50 and the bridges 6.

Note that the number of the excitation units 50 to be provided on thesoundboard 7 is not limited to two but may be larger or only one. Ifonly one excitation unit 50 is provided, preferably, the excitation unit50 is arranged at a position corresponding to the long bridge 6H.

The long bridge 6H is a bridge for supporting a predetermined group ofthe strings 5 corresponding a predetermined higher tone pitch range andthe short bridge 6L is a bridge for supporting a predetermined group ofthe strings 5 corresponding a predetermined lower tone pitch range.Hereinafter, if it is not especially necessary to distinguish betweenthe bridge 6H and the bridge 6L, the bridges will be expressed as justbridge 6. As described above, the excitation unit 50 is supported by thesupporting unit 55 connected to the straight supporting column 9.

[Construction of Excitation Unit 50]

FIG. 4 is a diagram, illustrating an appearance of the excitation unit50 according to the embodiment of the present invention. To represent amain structure of the yoke-holding unit 52 easily understandably, thisdiagram illustrates the interior of a casing 524 while omittingrepresentation of the casing 524 (see FIG. 5) of the yoke-holding unit52. The vibration member 51 has a cylindrical connecting member 511whose top face to be connected to the soundboard 7 is closed, and avoice coil 512. The connecting member 511 is made of a light weightmaterial like a resin such as polyimide or a metal such as aluminum, anda cap made of resin or the like is mounted to the top face thereof. Theyoke-holding unit 52 has the yokes 521, 523 which sandwich a magnet 522.The yokes 521, 523 are made of a soft magnetic material, for example,soft iron and much heavier than the connecting member 511. The vibrationmember 51 and the yoke-holding unit 52 are disposed apart from eachother via a space or air gap. That is, the yoke-holding unit 52 iscoupled magnetically with the voice coil 512 via an air gap.

FIG. 5 is a cross-sectional view of the excitation unit 50 shown in FIG.4, taken along a vertical plane passing through the center of theconnecting member 511, as seen from a horizontal direction. FIG. 5depicts the casing 524 also, whose representation is omitted in FIG. 4.In FIG. 5, positions of the soundboard 7 and the bridge 6 arerepresented with a dashed line to indicate a positional relationshipbetween the excitation unit 50, the soundboard 7 and the bridge 6. Thevibration member 51 comprises the connecting member 511 and the voicecoil 512 wound around the connecting member 511. In a whole magneticpath (indicated with a dashed line having an arrow) formed by the yokes521, 523 and the magnet 522, the voice coil 512 is movably disposed in amagnetic path portion passing through a space formed between the yoke521 and the yoke 523. The drive signal supplied to the excitation unit50 is input to the voice coil 512. Receiving a magnetic force from themagnetic path formed as described above, the voice coil 512 generates adrive force for vibrating the connecting member 511 in a verticaldirection in FIG. 5 according to a waveform indicated by the input drivesignal. Because the yoke-holding unit 52 is supported by the supportingunit 55 so that the position of the yoke-holding unit 52 is fixed, mostof all the drive force generated by the voice coil 512 is used as athrust force for vibrating the connecting member 511.

The top face of the connecting member 511 and the soundboard 7 arebonded to each other with adhesive or double-sided tape (notillustrated), so that the connecting member 511 is firmly fixed to thesoundboard 7. Connection between the connecting member 511 and the topface of the connecting member 511 is not limited to by bonding withadhesive, but may be by connection with a screw or the like.Consequently, when the connecting member 511 moves upward, thesoundboard 7 is pushed upward, and when the connecting member 511 movesdownward, the soundboard 7 is pulled downward by the connecting member511 without the connecting member 551's leaving the soundboard 7. Asdescribed above, due to the connection between the connecting member 511and the soundboard 7, the soundboard 7 is moved accurately both inpositive and negative directions in the drive waveform. As a result, avibration faithful to the waveform characteristics of a desired tone canbe produced in the soundboard 7. The vibration of the connecting member511 not only vibrates the soundboard 7, but also is propagated to thebridge 6 through the soundboard 7 and furthermore, to the string 5.

The casing 524 accommodates the yokes 521, 523 and the magnet 522. Thecasing 524 is supported by the supporting unit 55. In this way, theyoke-holding unit 52 constituted of the yokes 521, 523, the magnet 522and the casing 524 are disposed apart from the vibration member 51 viathe space or air gap and supported by the supporting unit 55 such thatthe yoke-holding unit 52 is not in contact with the soundboard 7. Asillustrated in FIG. 5, in this example, the supporting unit 55 supportsthe yoke-holding unit 52 from a bottom side of the casing 524. Becausethe vibration member 51 (connecting member 511) is disposed apart fromthe yoke-holding unit 52 via the space or air gap, it comes that thevibration member 51 is supported by the soundboard 7 when connected tothe soundboard 7.

Note that the fact that the vibration member 51 and the yoke-holdingunit 52 are separated from each other by the space means that in theillustrated configuration, the vibration member 51 and the yoke-holdingunit 52 are not in contact with each other. Instead, a partial structure(e.g., wiring leading to the voice coil 512) leading to the vibrationmember 51 may be in contact with the yoke-holding unit 52. At this time,it is desired that no load is applied from the yoke-holding unit 52 tothe vibration member 51 via that partial structure.

In this way, the yoke-holding unit (main body) 52 in the excitation unit50 is supported by the supporting unit 55, less or no load of theexcitation unit 50 except the vibration member 51 is applied to thesoundboard 7. The structure of the supporting unit 55 for supporting theyoke-holding unit 52 may be of any structure as long as no load exceptthe load of the vibration member 51 is applied to the soundboard 7.

As described above, the connecting member 511 is made of light materiallike resin, compared to the material of the yoke-holding unit 52. Theentire vibration member 51 including the connecting member 511 and thevoice coil 512 is formed of a very light weight structure compared tothe yoke-holding unit (main body) 52. Because a load of the yoke-holdingunit 52 is applied to the straight supporting column 9 via thesupporting unit 55, little load of the excitation unit 50 may be appliedto the soundboard 7. Although a load of the vibration member 51 acts onthe soundboard 7, this load is so slight that an influence thereof uponthe vibration characteristics of the soundboard is minimized.

[Construction of Voice Coil 512]

FIG. 6 is a diagram, illustrating the structure of the voice coil 512according to the embodiment of the present invention. FIG. 6 indicates aposition of the vibration member 51 when it is not vibrated.Hereinafter, the position of the vibration unit 51 when it is notvibrated is referred to as a standard position. A length in the verticaldirection (vibration direction of the vibration member 51) of the voicecoil 512 (hereinafter referred to as just a length of the voice coil512) is a sum of the length in the vertical direction of a magnetic pathspace 525 (hereinafter referred to as a magnetic path width mw) andupper and lower vibration partial lengths cw each corresponding to aneither end portion upper or lower than the magnetic path width mw. Thatis, the length of the voice coil 512 is a length which is a sum of themagnetic path width mw and a double of the vibration partial length cw.Although the magnetic path width mw is specified as a length equivalentto the thickness of the yoke 521 as illustrated in FIG. 6, actually,there exists a spread of a magnetic field. Thus, it is permissible toconsider that the spread is included in the magnetic path space 525 anddetermine the magnetic path width mw to be value larger than thethickness of the yoke 521 shown in FIG. 6.

FIGS. 7A to 7C are cross-sectional views illustrating vibrationconditions of the voice coil 512 in the embodiment of the presentinvention regarding three different dimensions of the voice coil 512. InFIGS. 7A to 7C, a reference sw indicates an amount of deflection (i.e.,a maximum deflection amount sw) from the standard position of thevibration member 51 when the drive signal of a maximum amplitude isinput to the voice coil 512 under a condition that the connecting member511 is connected to the soundboard 7. In FIGS. 7A to 7C, relativedimensions of the length of the voice coil 512 with respect to themagnetic path width mw are different from each other. That is, FIG. 7Aindicates a case where the vibration partial length cw is equal to themaximum deflection amount sw. FIG. 7B indicates a case where thevibration partial length cw is shorter than the maximum deflectionamount sw. FIG. 7C indicates a case where the vibration partial lengthcw is longer than the maximum deflection amount sw. In each of FIGS. 7Ato 7C, a diagram located at the left thereof indicates a state in whichthe vibration member 51 is at the standard position, a diagram locatedat the middle thereof indicates a state in which the vibration member 51is moved upward by the maximum deflection amount sw, and a diagramlocated at the right thereof indicates a state in which the vibrationmember 51 is moved downward by the maximum deflection amount sw.

As illustrated in FIG. 7A, in which cw=sw, when the deflection of thevibration member 51 is maximum upward, a bottom end bm of the voice coil512 is located at a bottom end of the magnetic path space 525. When thedeflection of the vibration member 51 is maximum downward, a top end tpof the voice coil 512 is located at a top end of the magnetic path space525. In this case, a portion having a length equivalent to the magneticpath width mw in the voice coil 512 is always situated in the magneticpath space 525. Thus, the vibration member 51 can obtain a drive forcestable regardless of the magnitude of the deflection during theexcitation.

As illustrated in FIG. 7B, in which cw<sw, when the deflection of thevibration unit 51 is maximum upward, the bottom end bm of the voice coil512 is located within the magnetic path space 525. When the deflectionof the vibration member 51 is maximum downward, the top end tp of thevoice coil is located within the magnetic path space 525. In this case,when the deflection of the vibration unit 51 is increased, a lengthlocated within the magnetic path space 525 of the voice coil 512 isshorter than the magnetic path width mw. Thus, a drive force whichshould be obtained from the drive signal may not be obtainedsufficiently. However, when no large drive signal which causes thevibration member 51 to reach the maximum deflection is input, thevibration member 51 can obtain a stable drive force like when cw=sw.

On the other hand, when the length of the voice coil 512 is decreased asshown in FIG. 7B, the number of windings per a unit length must bechanged. Because the number of the windings of the coil is decreased andinductance is decreased, there occurs an effect that an excellentresponsiveness can be obtained even in a high frequency range.

As illustrated in FIG. 7C, in which cw>sw, when the deflection of thevibration member 51 is maximum upward also, the bottom end of the voicecoil 512 is located out of the magnetic path space 525. When thedeflection of the vibration member 51 is maximum downward, the top endtp of the voice coil 512 is located out of the magnetic path space 525.In this case, like when cw=sw, a portion having a length equivalent tothe magnetic path width mw in the voice coil 512 is always locatedwithin the magnetic path space 525. Thus, the vibration member 51 canobtain a drive force stable regardless of the magnitude of thedisplacement of the vibration member 51 during the excitation.

On the other hand, in the voice coil 512, a portion located out of themagnetic path space 525 does not contribute to the drive force.Furthermore, if the length of the voice coil 512 is increased as shownin FIG. 7C, the number of windings of the coil increases unless thenumber of windings per a unit length is changed, thereby increasinginductance. Consequently, a frequency band in which an excellentresponsiveness can be obtained is limited to a low frequency band.

As described above, in case where cw>sw, the responsiveness in a highfrequency band is deteriorated and there is no advantageous factor,compared to the case where cw=sw. Therefore, according to the embodimentof the present invention, it is determined that the vibration partiallength cw is equal to or smaller than the maximum deflection amount sw.That is, the length of the voice coil 512 is determined to be equal toor smaller than a sum of the magnetic path width mw and a double of themaximum deflection amount sw. To make the vibration partial length cwshorter than the maximum deflection amount sw, an appropriate design ismade considering an amplitude of the vibration member 51 which generallycan occur when the soundboard 7 is vibrated, and a frequency bandcontained in the drive signal.

[Construction of Yokes 521, 523]

FIGS. 8A to 8C are cross-sectional views, illustrating a relationshipbetween the top face of the yoke 521 (hereinafter referred to as a platetop face), the top face of the voice coil 512, and the top face of apole of the yoke 523 (hereinafter referred to as a pole top face). FIG.8A indicates a case where when the vibration unit 51 is deflected upwardby the maximum deflection amount sw, the height of the pole top face isset to the same position as the top end of the voice coil 512. FIG. 8Bindicates a case where when the vibration unit 51 is situated at thestandard position, the height of the pole top face is set to the sameposition as the top end of the voice coil 512. FIG. 8C indicates a casewhere the height of the pole top face is set to the same position as theplate top face. It should be noted that in any case of FIGS. 8A to 8C,the length of the voice coil 512 is assumed to be a sum of the magneticpath width mw and a double of the vibration partial length cw. In eachof FIGS. 8A to 8C, a diagram located at the left thereof indicates astate in which the vibration unit 51 is situated at the standardposition, a diagram located at the middle thereof indicates a state inwhich the vibration unit 51 is moved upward by the maximum deflectionamount sw, and a diagram located at the right thereof indicates a statein which the vibration unit 51 is moved downward by the maximumdeflection amount sw.

In the case indicated in FIG. 8A, when the deflection of the vibrationunit 51 is maximum upward, the top end of the voice coil generally nevercomes out of a magnetic path formed between the plate top face and thepole top face. Thus, if a position of the pole top face is set to thestate illustrated in FIG. 8A, when a large drive signal is input to thevoice coil 512, an excellent response can be obtained.

In the case indicated in FIG. 8B, when the vibration unit 51 is at thestandard position, the top end of the voice coil 512 generally nevercomes out of a magnetic path formed between the plate top face and thepole top face. Although in the case indicated in FIG. 8A, when thevibration unit 51 is at the standard position, there exists a magneticflux which bypasses the voice coil, escaping upward, the case indicatedin FIG. 8B has no such bypassing magnetic flux. Therefore, when theposition of the pole top face is set to the state indicated in FIG. 8B,an excellent response is obtained when a vibration is started (whenstarting generation of sound).

In the case indicated in FIG. 8C, even when the deflection of thevibration unit 51 is maximum downward, the top end of the voice coil 512generally never comes out of a magnetic path formed between the platetop face and the pole top face. Although in the case of FIG. 8B, whenthe vibration unit 51 descends below the standard position, there isgenerated a magnetic flux which bypasses the voice coil 512, escapingupward, the case of FIG. 8C has no such bypassing magnetic flux. Thus,when the position of the pole top face is set to the state indicated inFIG. 8C, a stable response can be obtained regardless of the magnitudeof the amplitude.

If the height of the pole top face is higher than a height indicated inFIG. 8A, a magnetic flux which always bypasses the voice coil 512,escaping upward is generated regardless of the position of the vibrationunit 51. Therefore, there is no advantageous factor. Further, if theheight of the pole top face is lower than a height indicated in FIG. 8C,a magnetic flux is deviated downward. Consequently, drive forcegenerated in the vibration unit 51 becomes asymmetrical in the verticaldirection and thus, there is no advantageous factor. Therefore, it isdesirable that the height of the pole top face is lower than a positionof the top end of the voice coil 512 in a state where the vibration unit51 is deviated upward by the maximum deflection amount sw and higherthan the height of the plate top face.

The aforementioned construction of the yoke-holding unit (namely, mainbody) 52 is summarized as follows. The yoke-holding unit (main body) 52comprises the yoke (a first yoke) 521 is formed of a ring-shaped softmagnetic material and disposed on an upper surface of the magnet 522 andthe yoke (a second yoke) 523 is formed of a soft magnetic material.Here, it should be noted that an upside of the yoke-holding unit (mainbody) 52 or magnet 522 refers to a side near to the soundboard 7, evenif the yoke-holding unit (main body) 52 or magnet 522 will be arrangedin any direction. The second yoke 523 comprises a disk-shaped base unitconfigured to receive an underside surface of the magnet 522 on an uppersurface of the base unit and the pole (a cylindrical pole) extendingupwardly from a center portion of the base unit in such a manner thatthe pole is accommodated in an inner hollow portion of the magnet 522,the magnetic path space 525 is formed between an inside surface of thefirst yoke 521 and an outside surface of the pole, the vibration member51 is vibrated along a longitudinal direction of the pole, and aposition in the longitudinal direction of an upper end of the pole isdetermined so that the position is equal to or higher than a position anupper surface of the first yoke 521 and equal to or lower than aposition of a top end of the voice coil where the vibration member 51has been moved upward by the maximum deflection amount sw.

[Construction of Control Device 10]

FIG. 9 is a block diagram showing a construction of the control device10 in the instant embodiment of the invention. The control device 10includes a control unit 11, a storage unit 12, an operation panel 13, acommunication unit 14, a signal generation unit 15, and an interface 16,and these components are interconnected via a bus.

The control unit 11 includes an arithmetic unit such as centralprocessing unit (CPU), and the storage unit 12 includes a read-onlymemory (ROM), a random access memory (RAM), etc. The control unit 11controls the various components of the s control device 10 and variouscomponents connected to the interface 16 on the basis of a controlprogram stored in the storage unit 12. In the illustrated example, thecontrol unit 11 causes the control device 10 and some of the componentsconnected to the control device 10 to function as the keyboardinstrument, by executing the control program.

The storage unit 12 stores therein setting information indicative ofvarious settings for use during execution of the control program. Thesetting information is information for determining, on the basis ofdetection signals output from the key sensor 22, pedal sensor 23 andhammer sensor 24, content of the drive signal (audio waveform signal) tobe generated by the signal generation unit 15. The setting informationincludes information indicating sound generation mode and performancemode, which are set by the user.

The operation panel 13 includes, among other things, operation buttonsoperable by the user, i.e. capable of receiving user's operations. Oncea user's operation is received via any one of the operation buttons onthe operation panel 13, an operation signal corresponding to the user'soperation is output to the control unit 11. A touch panel 60 connectedto the interface 16 includes a display screen, such as a liquid crystaldisplay, and touch sensors for receiving user's operations are providedon a display section of the display screen. On the display screen aredisplayed, under control of the control unit 11 via the above-mentionedinterface 16, various kinds of information such as a setting changescreen for changing the content of the setting information stored in thestorage unit 12, a setting screen for setting any one of various modesand the like, and various information, such as a musical score. Thetouch panel 60 provides an operation screen of a user interface forreceiving a user's input. Once a user's operation is received via thetouch sensor, an operation signal corresponding to the user's operationis output to the control unit 11 via the interface 16. User'sinstructions to the control device 10 are input through user'soperations received via operations devices, including the operationpanel 13, touch panel 60 etc., and user interface associated with theoperations devices.

The communication unit 14 is an interface for performing communicationwith other devices in a wired and/or wireless fashion. To this interfacemay be connected a disk drive that reads out various data recorded on astorage medium, such as a DVD (Digital Versatile Disk) or CD (CompactDisk). Examples of data input to the control device 10 via thecommunication unit 14 include music piece data for use in an automaticperformance.

The signal generation unit 15 includes a sound source 151 configured tooutput an audio waveform signal, an equalizer unit 152 configured toadjust the frequency characteristics of the audio waveform signal, andan amplifying unit 153 configured to amplify the audio waveform signal(see FIG. 10). After the frequency characteristics are adjusted and theaudio waveform signal is amplified, the signal generation unit 15outputs the audio waveform signal as the drive signal.

The interface 16 is an interface that interconnects the control device10 and individual external components. Examples of the componentsconnected to the interface 16 include the key sensor 22, pedal sensor23, hammer sensor 24, key drive unit 30, stopper 40, excitation unit 50and touch panel 60. The interface 16 supplies the control unit 11 withdetection signals output from the key sensor 22, pedal sensor 23 andhammer sensor 24 and operation signals output from the touch panel 60.Further, the interface 16 supplies the key drive unit 30 and stopper 40with a control signal output from the control unit 11, and it suppliesthe excitation unit 50 with the audio waveform signal output from thesignal generation unit 15.

The following describe the acoustic grand piano 1 whose functions areimplemented by the control unit 11 executing the control program.

[Functional Construction of Grand Piano 1]

FIG. 10 is a block diagram showing a functional construction of thegrand piano 1 according to the embodiment of the present invention. Asillustrated in FIG. 10, when the key 2 is operated, the hammer 4 strikesthe string 5 so that the string 5 is vibrated. This vibration ispropagated to the soundboard 7 through the bridge 6. The damper 8 isactuated when the key 2 or the pedal 3 is operated. Due to the action ofthe damper 8, a prevention condition of the vibration of the string 5 isswitched.

A setting unit 110 is realized by a combination of the touch panel 60and the control unit 11, as a configuration having a function describedbelow. First, the touch panel 60 receives a user's operation for settinga desired sound generation mode. The control unit 11 changes settinginformation in response to a performance mode and a sound generationmode set by the user, and in response to these modes, outputs a controlsignal indicating the selected sound generation mode to a performanceinformation generation unit 120 and a prevention control unit 130.

The touch panel 60 receives a user's operation for setting variouscontrol parameters for the signal generation unit 15. The variouscontrol parameters include parameters which determine a tone color of asound represented by the audio waveform signal output from the soundsource 151, an adjustment condition of the frequency characteristics inthe equalizer unit 152, and an amplification factor of the amplificationunit 153.

Each of the control parameters may be set by the user individually, oralternatively, a plurality sets of the control parameters may bepreviously stored in the storage unit 12 so that the user can select adesired one set from the stored sets and thus the control parameterscorresponding to the selected set are set. The control unit 11 changesthe setting information corresponding to each control parameter set by auser and controls the drive signal to be generated by the signalgeneration unit 15 according to the control parameter. Alternatively,the equalizer unit 152 and the amplification unit 153 may be configuredto use only previously set control parameters while the change of theparameters through the control unit 11 is prevented.

The performance information generation unit 120 is realized, as aconfiguration having a function described below, by a combination of thecontrol unit 11, the key sensor 22, the pedal sensor 23 and the hammersensor 24. Behaviors of the key 2, the pedal 3 and the hammer 4 aredetected by the key sensor 22, the pedal sensor 23, and the hammersensor 24. Based on a resultant detection signal output, the controlunit 11 specifies the string-striking time point at which the hammer 4has struck the string 5 (i.e., key-on event time point), the key numberidentifying the operated key 2 corresponding to the struck string 5, thestriking velocity, and the vibration-suppressing time point (key-offevent time point) at which the damper 8 has suppressed vibration of thestring 5, as information (performance information) for use in the soundsource 151. In the illustrated example, the control unit 11 specifiesthe string-striking time point and the key number of the operated key 2with reference to the behavior of the key 2. Then, the striking velocityis specified with reference to the behavior of the hammer 4, and thevibration-suppressing time point is specified with reference to thebehavior of the key 2 and the pedal 3. It should be noted that thestring-striking time point may be specified according to the behavior ofthe hammer 4 and the striking velocity may be specified according to thebehavior of the key 2. The performance information may be informationformulated by musical instrument digital interface (MIDI) type controlparameter.

At the specified key-on event time point, the control unit 11 outputsperformance information indicative of the key number, the velocity andthe key-on event to the sound source 151. At the key-off event timepoint, the control unit 11 outputs performance information indicative ofthe key number and the key-off event to the sound source 151. When thesound generation mode set by the user is the sound damping mode or thesound intensifying mode (i.e., special sound generation mode), thecontrol unit 11 realizes the above-described function, and when it isthe normal sound generation mode, in the illustrated example, thecontrol unit 11 refrains from outputting performance information to thesound source 151. It should be noted that when the normal soundgeneration mode is selected, it is just necessary to prevent the signalgeneration unit 15 from generating and outputting any drive signal.Thus, even in a configuration for generating and outputting theperformance information, the control unit 11 only has to control thesignal generation unit 15 not to generate and output any drive signal.

The prevention control unit 130 is realized by the control unit 11 sothat the control unit 11 is configured to perform such a preventioncontrol function (namely, a function of the prevention control unit 130)as mentioned below. When a sound generation mode selected by the user isthe sound damping mode, the control unit 11 moves the stopper 40 to aposition for blocking the hammer 4 to strike the string 5 (namely, theblocking or preventing of the hammer 4 striking on the string 5 ispermitted), and when the normal sound generation mode or the soundintensifying mode is selected, the control unit 11 moves the stopper 40to a position where the striking of the string 5 by the hammer 4 is notblocked (namely, the blocking or preventing of the hammer 4 striking onthe string 5 is not permitted).

The sound source 151 generates the audio waveform signal based on theperformance information generated from the performance informationgeneration unit 120 (control unit 11). For example, the sound source 151generates the audio waveform signal having a tone pitch corresponding tothe key number and a sound volume corresponding to the velocity. Theaudio waveform signal is adjusted in accordance with frequencycharacteristics in the equalizer unit 152 and amplified by theamplification unit 153, and then the amplified signal is supplied to theexcitation unit 50 as the drive signal. As described above, theexcitation unit 50 vibrates in response to the supplied drive signal tovibrate the soundboard 7. Additionally, the vibration of the soundboard7 is propagated to the bridge 6 and then to the string 5 through thebridge 6. In this way, by generating the audio waveform signal havingthe tone pitch (frequency) corresponding to the key number of theoperated key for performance, the vibration sound generated from thesoundboard 7 (i.e., the actively-vibrated-soundboard sound) whichvibrates according to this audio waveform signal (drive signal) becomesto have a sound pitch corresponding to the sound pitch of the operatedkey. Furthermore, it is available to perform a velocity control (soundvolume control responsive to a key touch) on the vibration sound fromthe soundboard 7. However, the frequency of the audio waveform signal(drive signal) can be changed in various ways not limited to theillustrated example. For example, it is possible to generate a mixedsignal by mixing audio waveform signals each having different tonepitches like chord tones and then vibrate the soundboard 7 using themixed signal as the drive signal.

FIG. 11 illustrates a modification of the embodiment illustrated in FIG.10 in case where two excitation units 50H, 50L are used. FIG. 11 is thesame as FIG. 10 except that two excitation units 50H, 50L are providedand frequency characteristics specifying unit 155 is added.

In the example illustrated in FIG. 11, the sound source 151 outputs anaudio waveform signal (hereinafter referred to as audio waveform signalH) for use as the drive signal (hereinafter referred to as drive signalH) to be input to the excitation unit 50H, and an audio waveform signal(hereinafter referred to as audio waveform signal L) for use as a drivesignal (hereinafter referred to as a drive signal L) to be input to theexcitation unit 50L, via two different systems.

The audio waveform signal H and the audio waveform signal L may be ofthe same signal or different from each other. For example, the audiowaveform signal H and the audio waveform signal L may be different fromeach other in terms of a frequency band. For example, the frequency bandof the audio waveform signal H may be higher than that of the audiowaveform signal L. Further, each channel of a plurality of channels suchas right and left channels of stereo may be allocated to any one of theaudio waveform signals H, L.

In the example illustrated in FIG. 11, the equalizer unit 152 adjuststhe frequency characteristics of the audio waveform signal H and theaudio waveform signal L respectively and outputs their results. Theadjustment condition of the frequency characteristics with respect tothe audio waveform signal H is specified by the frequency characteristicspecifying unit 155 corresponding to the vibration characteristics ofthe soundboard 7 at a connection position (hereinafter referred toconnection position H) of the vibration member 51 to the soundboard 7,included in the excitation unit 50H. Further, the adjustment conditionof the frequency characteristics with respect to the audio waveformsignal L is specified by the frequency characteristic specifying unit155 corresponding to the vibration characteristics of the soundboard 7at a connection position (hereinafter referred to as connection positionL) of the vibration member 51 to the soundboard 7, included in theexcitation unit 50L. An example of the adjustment condition of thefrequency characteristics will be described with reference to FIGS. 12Aand 12B.

FIGS. 12A and 12B are graphs illustrating an adjustment condition offrequency characteristics in the equalizer unit 152. FIG. 12Aillustrates the adjustment condition of the frequency characteristics(hereinafter referred to as frequency characteristics H) with respect tothe audio waveform signal H in the equalizer unit 152, and FIG. 12Billustrates the adjustment condition of the frequency characteristics(hereinafter referred to as frequency characteristics L) with respect tothe audio waveform signal L in the equalizer unit 152.

The frequency characteristics H is determined in inverse relation tovibration characteristics of the soundboard 7 at a connection positionof the vibration member 51 of the excitation unit 50H to the soundboard7 in such a manner that so as to suppress levels at frequency bands ofthe frequency characteristics H corresponding to resonance frequencybands of under a the vibration characteristics of the soundboard 7 aresuppressed to thereby prevent the volume of theactively-vibrated-soundboard sound from increasing at the frequencybands corresponding to the resonance frequency bands, but levels atfrequency bands of the frequency characteristics H corresponding to dipfrequency bands of the vibration characteristics of the soundboard 7 areenhanced to thereby prevent the volume of theactively-vibrated-soundboard sound from decreasing at the frequencybands corresponding to the dip frequency bands. In the example as shownin FIG. 12A, frequency bands of dips D1, D2 in the frequencycharacteristics H correspond to frequency bands of resonance peaks inthe vibration characteristics of the soundboard 7 at the connectionposition. Also, a frequency band of peak P1 in the frequencycharacteristics H corresponds to a frequency band of a dip in thevibration characteristics of the soundboard 7 at the connectionposition. It should be noted that the frequency characteristics H is notnecessarily determined in completely inverse relation to vibrationcharacteristics of the soundboard 7 at the connection position of thevibration member 51. For example, any one of such dips D1, D2 and peakP1 may not exist in the frequency characteristic H in FIG. 12A.

Further, in the exemplary frequency characteristics H as shown in FIG.12A, in order to address a demerit that a high-frequency characteristicof excitation by the excitation unit 50 drops due to an influence ofinductance of the voice coil 512, a gain-enhanced area S1 where a gainin a high frequency band of the frequency characteristics H is increasedis defined. It should be noted that such the gain-enhanced area S1 maybe omitted.

In this way, the audio waveform signal H has the frequencycharacteristics H in which amplitude level components at the frequencybands corresponding to the resonance peaks of the vibrationcharacteristics of the soundboard 7 are suppressed by provision of thedips D1, D2, amplitude level components at the frequency bandcorresponding to the dip of the vibration characteristics of thesoundboard 7 are enhanced by provision of the peak P1 to thereby preventfrom being reduced in volume, and amplitude level components at the highfrequency band are enhanced so that the influence of inductance of thevoice coil 512 is suppressed. The audio waveform signal H is amplifiedby the amplification unit 153, and then the amplified signal is suppliedto the excitation unit 50H as a drive signal H. As a result, the drivesignal H is supplied to the excitation unit 50H as a signal havingfrequency characteristics determined in such a manner as to suppressinfluences of resonance peaks and dips of the soundboard 7 at theconnection position H. Further, if the gain-enhanced area S1 is set inthe frequency characteristics H, the reduction of amplitude levelcomponents in the high frequency band due to an influence of inductanceof the voice coil 512 can be compensated.

On the other hand, in the similar manner as mentioned above, thefrequency characteristics L is determined in inverse relation tovibration characteristics of the soundboard 7 at a connection positionof the vibration member 51 of the excitation unit 50L to the soundboard7. Namely, levels at frequency bands of the frequency characteristics Lcorresponding to resonance frequency bands of the vibrationcharacteristics of the soundboard Tare suppressed to thereby prevent thevolume of the actively-vibrated-soundboard sound from increasing at thefrequency bands corresponding to the resonance frequency bands, butlevels at frequency bands of the frequency characteristics Lcorresponding to dip frequency bands of the vibration characteristics ofthe soundboard 7 are enhanced to thereby prevent the volume of theactively-vibrated-soundboard sound from decreasing at the frequencybands corresponding to the dip frequency bands. In this example, thefrequency band of dip D3 in the frequency characteristics L correspondsto a frequency band of a resonance peak in the vibration characteristicsof the soundboard 7 at the connection position. Also, the frequencybands of peaks P1, P3 in the frequency characteristics L correspond tofrequency bands of dips in the vibration characteristics of thesoundboard 7 at the connection position. It should be noted that thefrequency characteristics L is not necessarily determined in completelyinverse relation to vibration characteristics of the soundboard 7 at theconnection position of the vibration member 51. For example, any one ofsuch a dip D3 and peaks P2, P3 may not exist in the frequencycharacteristic L in FIG. 12B.

As same as mentioned above, in the exemplary frequency characteristics Las shown in FIG. 12B, in order to address to the demerit that thehigh-frequency characteristic of excitation by the excitation unit 50drops due to the influence of inductance of the voice coil 512, again-enhanced area S2 where a gain in a high frequency band of thefrequency characteristics L is increased is defined. Also, thegain-enhanced area S2 can be omitted.

In this way, the audio waveform signal L has the frequencycharacteristics L in which amplitude level components at the frequencyband corresponding to the resonance peak of the vibrationcharacteristics of the soundboard 7 are suppressed by provision of thedip D3, amplitude level components at the frequency bands correspondingto the dips of the vibration characteristics of the soundboard 7 areenhanced by provision of the peaks P2, P3 to thereby prevent from beingreduced in volume, and amplitude level components at the high frequencyband are enhanced so that the influence of inductance of the voice coil512 is suppressed. The audio waveform signal L is amplified by theamplification unit 153, and then the amplified signal is supplied to theexcitation unit 50L as a drive signal L. As a result, the drive signal Lis supplied to the excitation unit 50L as a signal having frequencycharacteristics determined in such a manner as to suppress influences ofresonance peaks and dips of the soundboard 7 at the connection positionL. Further, if the gain-enhanced area S2 is set in the frequencycharacteristics L, the reduction of amplitude level components in thehigh frequency band due to an influence of inductance of the voice coil512 can be compensated.

In FIG. 11, the amplification unit 153 may amplify each of the audiowaveform signals H, L with the same amplification factor or with adifferent amplification factor from each other. The excitation units50H, 50L vibrate according to the drive signals H, L supplied theretorespectively so that the soundboard 7 is vibrated. The vibration of thesoundboard 7 is propagated to the bridge 6 and then to the string 5through the bridge 6.

The frequency characteristic specifying units 155 specifies thefrequency characteristics H and the frequency characteristics L, whichare to be adjusted by the equalizer unit 152, with respect to the drivesignal H and the drive signal L. FIG. 13 is a diagram illustrating amechanism in which the frequency characteristic specifying portion 155specifies the frequency characteristics H and the frequencycharacteristics L.

For example, prior to shipping the grand piano 1 as an individualproduct, a personnel in charge of product adjustment makes a specifiedoperation of instructing a specific processing about the frequencycharacteristics with the touch panel 60 provided on the same grand piano1, the signal generation unit 15 outputs an impulse signal to theexcitation unit 50H as a drive signal. The voice coil 512 of theexcitation unit 50H is driven strongly in an extremely short period bythe impulse signal input from the signal generation unit 15, so that thesoundboard 7 is vibrated via the connecting member 511. After thesoundboard 7 is excited, the soundboard 7 is vibrated like when it isstruck by one time with a hard object at the arrangement position of theexcitation unit 50H.

When the soundboard 7 is vibrated, the voice coil 512 is also vibratedin response to the vibration of the soundboard 7. When the voice coil512 arranged in the magnetic path formed by the yoke-holding unit 52 isvibrated, an electromotive force is generated between both ends of thevoice coil 512. To measure the value of a voltage generated by thiselectromotive force, a voltmeter 160 is connected between the both endsof the voice coil 512. The voltmeter 160 outputs the value of voltagebetween the both ends of the voice coil 512 generated by a vibration ofthe soundboard 7, to the frequency characteristic specifying unit 155.

The frequency characteristic specifying unit 155 records voltage valuesinput sequentially from the voltmeter 160 and then, specifies thefrequency characteristics of waveforms (waveforms corresponding tovibration of the soundboard 7) indicated by a variation with time of therecorded voltage values by using a known method such as a Fouriertransformation. Such the specified frequency characteristics indicatethe vibration characteristics of the soundboard 7 at a position wherethe excitation unit 50H is connected to (connection position H). Inresponse to such the specified frequency characteristics at theconnection position H of the soundboard 7, the frequency characteristicspecifying unit 155 specifies (or determines) the frequencycharacteristics H for adjusting the drive signal to be output from theequalizer unit 152 to the excitation unit 50H in such a manner as toincrease the amplitudes of frequency components in the frequency bandcorresponding to the dip and suppress the amplitudes of frequencycomponents in the frequency band corresponding to the peak.

Subsequently, the signal output unit 15 outputs an impulse signal to theexcitation unit 50L as the drive signal. After that, the same processingas the processing applied to the excitation unit 50H as described aboveis carried out as to the excitation unit 50L. As a result, the frequencycharacteristic specifying unit 155 specifies (or determines) thefrequency characteristics L for adjusting a drive signal to be output tothe excitation unit 50L by the equalizer unit 152. The specifiedfrequency characteristics H, L are set in the equalizer unit 152.

[Example Behavior]

Next, a description will be given about example behavior of the grandpiano 1 employing the instant embodiment. First, the user operates thetouch panel 60 to set the performance mode as the normal performancemode and the sound generation mode as the sound damping mode. Under thiscondition, when the user operates the key 2 for a musical performance, astrike of the hammer 4 against the string 5 is blocked and thesoundboard 7 is vibrated by the excitation unit 50 so that theactively-vibrated-soundboard sound is radiated from the soundboard 7.Further, the bridge 6 is also vibrated via the soundboard 7, so thatother strings 5 than those prevented from being vibrated by the damper 8are also vibrated to generate a sound similar to the acoustic piano.Because a strike of the hammer 4 against the string 5 is blocked, nosound is generated by striking the string 5. Therefore, it is possibleto generate a sound using the vibration of the soundboard 7 and theacoustic effect due to the resonance of the strings like an acousticpiano with a smaller sound volume (or a larger sound volume) than asound generated by striking the string, by means of adjusting theamplitude of vibration of the excitation unit 50. Further, because thelength of the voice coil 512 is determined to be lower than the sum ofthe magnetic path width mw and the double of the maximum deflectionamount sw, responsiveness in the high frequency region can be improvedwhile securing the drive force for vibrating the soundboard 7effectively.

As described above, the excitation unit 50H excites the soundboard 7using the drive signal H having the frequency characteristics set tosuppress influences of the resonance peaks and dips of the soundboard 7at the connection position H. Also, the excitation unit 50L vibrates thesoundboard 7 using the drive signal L having the frequencycharacteristics set to suppress influences of the resonance peaks anddips of the soundboard 7 at the connection position L. Thus, In thekeyboard instrument (grand piano 1) having the excitation unit 50mounted on the soundboard 7, influence on a quality of the soundgenerated by the keyboard instrument due to the resonance of thesoundboard 7 can be controlled so that a sound having an unexpectedquality can be never generated. Further, according to the abovedescribed embodiments, it is capable of generating a sound havingrelatively flat frequency characteristics over an entire audio frequencyrange. Further more, according to the above described embodiments, it isnot necessary to use such an ordinary speaker for driving the soundboard7 that generates a sound by driving a cone paper. In this way, because asound can be generated even only by exciting the soundboard, a soundgeneration mechanism of a conventional acoustic piano can be usedeffectively thereby obtaining a natural acoustic effect.

On the other hand, when the normal sound generation mode is selected bythe user's operation of the touch panel 60, the excitation unit 50refrains from vibrating and striking the string 5 by the hammer 4 is notprevented. Thus, a sound is generated in response to striking the string5 and the vibration of the string 5 is transmitted to the soundboard 7via the bridge 6. The soundboard 7 radiates a sound corresponding to thevibration transmitted from the string 5. In this condition, only a loadof the vibration member 51, which is a very light component of theexcitation unit 50, is applied to the soundboard 7. Thus, the excitationunit 50 hardly affects the vibration characteristics of the soundboard7, so that the user can play the acoustic piano without impairing anoriginal acoustic property of the acoustic piano.

When the sound intensifying mode is selected by the user's operation ofthe touch panel 60, excitation of the soundboard 7 by means of theexcitation unit 50 and striking the string 5 by the hammer 4 are carriedout at the same time in response to an operation of key 2. Thus, thesoundboard 7 radiates a sound through vibration which is a sum ofvibration propagated from the struck string 5 to the soundboard 7 viathe bridge 6 and vibration of itself caused by the excitation unit 5.Upon struck by the hammer 4, the struck string 5 radiates the soundthrough vibration of itself and the other strings 5 which are notprevented by the damper 8 from vibrating are vibrated according to thepropagated vibration form the soundboard 7 to these strings 5 via thebridge 6 to thereby produce a resonance sound. Consequently, theoriginal sound of the acoustic piano and theactively-vibrated-soundboard sound generated via the soundboard 7according to the audio waveform signal output from the sound source 151are naturally mixed together to produce a performance soundcorresponding to the mixed sound.

Whereas the preceding paragraphs have described a preferred embodimentof the present invention, the present invention can be practiced invarious other manners as set forth below.

[Modification 1]

Whereas the preferred embodiment of the vibration member 51 (connectingmember 511) is completely separated from the yoke-holding unit 52, thevibration member 51 may be connected indirectly with the yoke-holdingunit 52 or casing 524.

FIG. 14 is a cross-sectional view of excitation unit 50A to whichmodification 2 of the present invention is applied. The excitation unit50A in the illustrated example includes a damper unit 53 configured toconnect the connecting member 511 with the casing 524. The damper unit53 is expanded and contracted following a vertical vibration of theconnecting member 511 from the standard position where the voice coil512 is not driven by the drive signal and no force is applied to thesoundboard 7 by the connecting member 511. In the illustrated example,in a condition that the connecting member 511 is not yet connected tothe soundboard 7 and is kept supported by only the damper unit 53, aheight of the supporting unit 55 for supporting the excitation unit 50Athereon is adjusted so that the top face of the connecting member 511 inthe standard position is just in contact with the bottom face of thesoundboard 7. Then, with this condition, the top face of the connectingmember 511 is connected to the bottom face of the soundboard 7.

In this way, in the standard position, no weight of the excitation unit50A is applied to the soundboard 7. The damper unit 53 is capable ofsupporting the light-weight vibration member 51 and highly stretchable.Therefore, when the soundboard 7 is vibrated, the weight of theyoke-holding unit 52 is hardly transmitted to the vibration member 51due to the damper unit 53, and there is less or no influence on thevibration characteristics of the soundboard 7 accordingly. Further,because the connection between the vibration member 51 and theyoke-holding unit 52 is kept due to existence of the damper unit 53, itis facilitated for a human worker to connect the excitation unit 50 tothe soundboard 7 during manufacturing steps.

[Modification 2]

Whereas the preferred embodiment of the grand piano 1 of the presentinvention has been described above as applied to a grand piano, it maybe applied to an upright piano.

FIG. 15 is a view showing an inner construction of an upright piano 1Bwhich employs modification 2 of the present invention is applied. InFIG. 15, elements of the upright piano 1B similar to the elements of thegrand piano 1 are indicated by the same reference numerals as used forthe grand piano 1 but each with suffix “B”. In the upright piano 1B too,the vibration member 51B in then excitation unit 50B is connected to thesoundboard 7B, and the yoke-holding unit 52B is supported by thesupporting unit 55B connected to the straight supporting column 9B.

FIG. 16 is a view explanatory of a positional arrangement of theexcitation unit 50B according to the modification 2. In the illustratedexample as well, the excitation unit 50B is connected to the soundboard7B located between ribs 75B. The excitation unit 50B is provided in aposition corresponding to the bridge 6B (in other words, back surface ofthe soundboard 7B at the position where the bridge 6B is mounted).Further, in the example illustrated in FIG. 16, although the supportingunit 55B is connected to a plurality of the straight supporting columns9B, the supporting unit 55B may be connected to one straight supportingcolumn 9B. Although the excitation unit 50B shown in FIG. 16 is providedon a position corresponding to a long bridge of the bridges 6B, theexcitation unit 50B may be located at a position corresponding to ashort bridge (not illustrated) of the bridges 6B. Further, the vibrationunits 50B may be provided on each position corresponding to the longbridge and the short bridge. With this arrangement, each one of the longand short bridges can be driven accurately and effectively with adesired vibration. Furthermore, there may be provided with one or moreexcitation units 50B at one or more suitable portions corresponding toeach of the long and short bridges.

[Modification 3]

Whereas, in the above-described preferred embodiment, the excitationunit 50 is supported by the supporting unit 55 so that no load exceptthe vibration member 51 is applied to the soundboard 7, other weightthan the vibration member 51 may be applied to. For example, thesupporting unit 55 may support the excitation unit 50 in a state inwhich it is connected to the soundboard 7. Alternatively, an excitationunit may be attached directly to the soundboard 7 without existence ofthe supporting unit 55. A case where no supporting unit 55 exists willbe described with reference to FIG. 17.

FIG. 17 is a side view showing a state in which an excitation unit 50Cis directly mounted onto the soundboard 7 employing modification 3 ofthe present invention. The excitation unit 50C comprises a vibrationmember 51C and connecting members 54C. The vibration member 51C isconnected to the soundboard 7 with the connecting member 54C such as ascrew. The vibration member 51C contains a weight inside which isconfigured to be vibrated in response to the drive signal input to thevibration member 51C so that the soundboard 7 is vibrated by reaction ofthe vibration of the weight.

In this case, because a weight of the entire excitation unit 50C isapplied to the soundboard 7, there is a possibility that the vibrationcharacteristics of the soundboard 7 may be varied from preferablecharacteristics if no compensation is applied. In view of this point,according to the modification 3 of the present invention, the frequencycharacteristics of the drive signal is determined in such a manner as tocompensate the varied vibration characteristics and reduce such aninconvenience. Further, in the modification 3, if the sound quality inthe normal sound generation mode is changed from a sound quality in acase where no excitation unit 50C is attached due to the variedvibration characteristics, such a change in the sound quality can beeliminated by exciting the excitation unit 50C with a suitable drivesignal in the normal sound generation mode so as to compensate thechange in the sound quality. Alternatively, it may be configured in themodification 3 not to use the normal sound generation mode.

[Modification 4]

Whereas, in the above-described preferred embodiment, the drive signalhas been obtained by adjusting the frequency characteristics of theaudio waveform signal in the equalizer unit 152, the drive signal may begenerated without adjusting through the equalizer unit 152. In thismodification 4 of the present invention, the sound source 151 isconfigured to generate the audio waveform signal H (or audio waveformsignal L) to have the preferable frequency characteristics correspondingto the drive signal H (or drive signal L). Then, the audio waveformsignal H (or audio waveform signal L) may be amplified by theamplification unit 153 and output as the drive signal H (or drive signalL).

[Modification 5]

In the above-described embodiment, the drive signal H (or drive signalL) has frequency characteristics having dips and peaks at frequencypositions corresponding to the resonance peaks and dips of the frequencycharacteristics of the soundboard 7 at the connection position H (orconnection position L). However, the drive signal may be a signal havingother frequency characteristics which are set so as to have further dipsand/or peaks at other frequency positions than the resonance peaks anddips. If there are the further dips and/or the peaks at other frequencypositions than the frequency positions of the resonance peaks and dips,generation of various sounds with a variety of tone colors can beachieved.

Various sets of the frequency characteristics each having a pattern ofan appropriate combination of dips and peaks may be previously stored inthe storage unit 12 so that the user can select a desired pattern to beset as the frequency characteristics of the drive signal by an operationof the touch panel 60 or the like. Further, it may be constructed insuch a manner that the user determines a pattern of a preferablecombination of dips and peaks to store the determined pattern in thestorage unit 12 as a new template. It should be noted that the frequencycharacteristics of the drive signal H and the frequency characteristicsof the drive signal L may be different from each other.

The drive signal is not limited to a signal set to suppress theresonance of the soundboard 7, it may be a signal having frequencycharacteristics set to emphasize the resonance. In this case, the drivesignal should not be formed so that a dip exists in the frequency bandcorresponding to the resonance peak of the soundboard 7, but should beformed so that a peak exists in the frequency band corresponding to theresonance peak of the soundboard 7. Similarly, the drive signal may notbe formed so that a peak exists in the frequency band corresponding tothe dip of the soundboard 7, but may be formed so that a dip exists inthe frequency band corresponding to the dip of the soundboard 7. In thisconnection, the frequency characteristics of the drive signal H may beset so that a dip exists in the frequency band corresponding to theresonance peak, while the frequency characteristics of the drive signalL may be set so that a peak exists in the frequency band correspondingto the resonance peak.

In this way, the drive signal to be input to each of a plurality of theexcitation unit 50 may be any kind of signal as long as it is a signalhaving frequency characteristics associated with the vibrationcharacteristics of the soundboard 7 in the position where the vibrationmember 51 included in the excitation unit 50 to be input thereto thedrive signal is connected.

[Modification 6]

Whereas, in the above-described preferred embodiment, the frequencycharacteristics of the drive signal H (or drive signal L) is previouslyset so that the dip and the peak exists in the frequency bandcorresponding to the resonance peak and the dip of the soundboard 7 atthe connection position H (connection position L), if a mountingposition of the excitation unit 50H (excitation unit 50L) is changed,the frequency characteristics of the drive signal may be modified sothat the frequency and magnitude of the dip and peak (hereinafterreferred to setting parameter) may be changed. The setting parameter maybe set by a user's operation of the touch panel 60 or the like.Alternatively, it may be constructed in such a manner that, in responseto a user's instruction through the touch panel 60 or the like todesignate a position of the excitation unit 50 to be mounted on thesoundboard 7 (e.g., coordinate position on the soundboard 7), thecontrol unit 11 calculates necessary setting parameters to be set basedon the designated position and information indicative of the vibrationcharacteristics of the soundboard 7 which is previously set (suchinformation includes e.g., an arithmetic expression indicating arelationship between the designated coordinate position and thevibration characteristics).

[Modification 7]

Whereas, in the above-described preferred embodiment, the excitationunit is provided at a position corresponding to the bridge on thesoundboard, the excitation unit may be provided at any positiondistanced from the bridge. FIG. 18 is a view explanatory of anarrangement of the excitation unit according to modification 7 of thepresent invention in which the upright piano according to themodification 2 shown in FIG. 15 is modified in such a manner that theexcitation units 50B are arranged at positions distanced from the bridge6B on the soundboard 7B. In the illustrated example of FIG. 18, twoexcitation units 50B are arranged at positions (rear face of thesoundboard 7B in FIG. 18) opposing the ribs 75B across the soundboard7B.

FIG. 19 is a view explanatory of an internal construction of the uprightpiano according to modification in which the excitation unit 50B asshown in FIG. 18 is supported by the supporting unit 55B. As shown inFIG. 19, the supporting unit 55B of the modification 7 has a two-angledshape formed by bending a plate, e.g., a stainless plate, by a rightangle toward opposite directions at two different positions in alongitudinal direction respectively. A flat portion constituting one endportion of the supporting unit 55B is attached to the back face of ashelf plate 90 of the upright piano 1B by a screw or the like. Theyoke-holding unit 52B of the excitation unit 50B is attached to anotherflat portion constituting another end portion of the supporting unit55B. The yoke-holding unit 52B is disposed at a position opposing therib 75B across the soundboard 7B and the yoke-holding unit 52Baccommodates the vibration member 51B connected to the soundboard 7B atthat position.

Even in the above-described configuration in which the excitation unitis connected to the soundboard at the position corresponding to not thebridge but the rib, the vibration caused by the excitation unit ispropagated to the entire soundboard through the rib effectively, so thata desired radiation of a sound via the soundboard is achieved.

Further, it may be constructed in such a manner that there is providedwith an excitation rod, which is a rod-like member different from therib, on the front surface of the soundboard which is an opposite side tothe rear surface of the soundboard where the rib is provided, and theexcitation unit at a position opposing the excitation rod across thesoundboard, namely on the rear surface of the soundboard. Because theexcitation rod can be designed separately from an existing bridge orrib, it is desirable to adjust the shape, size, arrangement position andthe like of the excitation rod so that a sound having desired audiocharacteristics is radiated in response to excitation by the excitationunit.

Furthermore, the excitation unit may be disposed at any position on thesoundboard other than the position corresponding to the bridge, rib orexcitation rod as described above, as long as a preferable vibrationsound can be radiated from the disposed position on the soundboard.

[Modification 8]

Whereas, in the above-described preferred embodiment, the yoke-holdingunit 52 is assumed to generate the magnetic field using the magnet 522consisting of a permanent magnet, a construction such as anelectromagnet capable of controlling generation of the magnetic fieldcan be used instead of the permanent magnet so that the generation ofthe magnetic field can be stopped when the vibration member 51 shouldnot be vibrated, e.g., in the normal sound generation mode.

[Modification 9]

Whereas, in the above-described preferred embodiment, the excitationunit 50 has the vibration member 51 and the yoke-holding unit 52, and isconstructed in a configuration similar to dynamic type speaker using thevoice coil, the configuration of the excitation unit of the presentinvention is not limited to the configuration similar to the dynamictype speaker. Any other configuration may be adopted such that theexcitation unit has a main body and a vibration unit which is lighterthan the main body, separated from the main body and connected to thesoundboard and at least one of attraction force, and that repulsionforce in response to the drive signal is generated between the main bodyand the vibration unit.

FIG. 20 is a cross-sectional view explanatory of an excitation unitaccording to modification 9 of the present invention, in which theexcitation unit is configured in a different way from the dynamic typespeaker. An excitation unit 80 of the modification 9 comprises amagnetic sheet 81, as the vibration member, consisting of a sheet-likeferromagnetic material attached to the soundboard 7 and an electromagnet82, as the main body, supported by the supporting unit 55. Theelectromagnet 82 comprises a core 821 made of a cylindrical magneticmaterial and a coil 822 wound around the core 821 and generates magneticforce whose intensity and polarity change according to the drive signalinput from the control unit 10.

The magnetic sheet 81 causes the soundboard 7 to vibrate in accordancewith attraction force and repulsion force produced by the magnetic forcefrom the electromagnet 82. It is preferable that the magnetic sheet 81is made of a ferromagnetic material from which not only attraction forceproduced in a direction approaching toward the electromagnet 82 but alsorepulsion force produced in a direction leaving from the electromagnet82 can be obtained in response to the magnetic force generated from theelectromagnet 82. However, the magnetic sheet 81 may be made of aparamagnet or a diamagnetic material rather than the ferromagneticmaterial. In this case, the soundboard 7 receives such a force only inone direction, that is, the direction toward the electromagnet 82 (incase of paramagnetic material) or the direction off the electromagnet 82(in case of diamagnetic material) and when the soundboard receives theforce from the magnetic sheet 81, it is moved from its steady-stateposition, and when the force from the magnetic sheet 81 is released, itis moved toward the steady-state position by a restoring force, therebythe soundboard is vibrated.

Of the excitation unit 80, only a weight of the light magnetic sheet 81is applied to the soundboard 7 but the weight of the electromagnet 82,which occupies most weight of the excitation unit 80, is not applied tothe soundboard 7. Thus, the excitation unit 80 hardly affects thevibration characteristic of the soundboard 7.

In summary, according to the modification 9, the vibration member isformed of the sheet-like magnetic material (81) attached to thesoundboard 7, and the excitation unit includes the electromagnet (82)which is magnetically coupled with the sheet-like magnetic material viaair gap and excited by the drive signal. The supporting unit 55 supportsthe electromagnet.

[Modification 10]

Whereas, in the above-described preferred embodiment, the supportingunit 55 supports the excitation unit 50 in a state in which thesupporting unit 55 is connected to the straight supporting column 9, thesupporting unit 55 may be connected to other than the straightsupporting column 9. For example, the supporting unit 55 may support theexcitation unit 50 in a state in which the supporting unit 55 isconnected to a side plate or leg of the grand piano 1. Further, thesupporting unit 55 may support the excitation unit 50 in a state inwhich the supporting unit 55 is connected to a construction (e.g.,floor, wall) of a room where the grand piano 1 is placed.

Although the supporting unit 55 supports the excitation unit 50 suchthat no load except the vibration member 51 is applied to the soundboard7, other weight than the vibration member 51 may be applied thereto. Forexample, the connecting member 511 of the excitation unit 50A of themodification 1 may be urged upward or downward by the damper unit 53 ina state in which the soundboard 7 is not being vibrated.

[Modification 11]

The control program of the above-described embodiment may be provided ina state in which the control program is stored in a computer readablerecording medium such as a magnetic recording medium (magnetic tape,magnetic disk), an optical recording medium (optic disk), amagnet-optical recording medium, and a semiconductor memory. Further,for the grand piano 1, the control program may be downloaded via anetwork.

[Modification 12]

Whereas, in the above-described preferred embodiment, as the shape ofthe connecting member 511, a cylindrical shape having a substantiallyidentical diameter to the diameter of the voice coil 512 is adopted, theshape of the connecting member 511 is not limited to this example. FIG.21 is a diagram, illustrating an example of the excitation unit of thepresent invention having the connecting member 511 having a notcylindrical shape. The connecting member 511 of the excitation unit 50illustrated in FIG. 21 includes a hollow, cylindrical main body 5111whose top face is closed and whose bottom face is open, and acylindrical supporting rod 5112 whose bottom face is attached to the topface of the main body 5111 such that the supporting rod is extendedupward from the center of the top face of the main body 5111. The topface of the supporting rod 5112 is connected to the bottom face of thesoundboard 7 and the soundboard 7 is vibrated by the top face of thesupporting rod 5112.

According to the excitation unit 50 having the connecting member 511having the shape as shown in FIG. 21, the rib 75 is arranged near adesired position (e.g., a position corresponding to the bridge 6) wherethe excitation unit 50 is desired to be disposed. Even if the shape ofthe connecting member 511 of the above-described embodiment interfereswith the rib 75, the connecting member 511 of the modification 12 can beconnected to the soundboard 7 as long as the supporting rod 5112 doesnot interfere with the rib 75.

[Modification 13]

As modification 13, the yoke-holding unit 52 of the above-describedembodiment can be modified in such a manner as to provide with anothermagnet in addition to the magnet 522 in order to increase magnetic fluxpassing through the magnetic path space 525. FIGS. 22A, 22B arecross-sectional views explanatory of an excitation unit according to themodification. In FIGS. 22A and 22B, ring-like magnets 526, 523 arearranged on the top face of the yoke 521 and the bottom face of the yoke523 respectively so as to oppose the magnet 522. In the modification 13illustrated in FIG. 22B, a further magnet 528 is arranged on the topface of a pole of the yoke 523.

In FIGS. 22A and 22B, the magnets 526, 527 are arranged such that thepolarities are opposite to the polarity of the magnet 522. The magnet528 is arranged such that the polarity is in the same as the polarity ofthe magnet 522. With this arrangement, magnetic flux intending to leakupward from the yoke 521 and magnetic flux intending to leak downwardfrom the yoke 523 are introduced into the magnetic path by the magnet527. As a result, leakage magnetic flux is reduced so that magnetic fluxpassing through the magnetic path space 525 is increased. It should benoted that it is not necessary to provide with both the magnets 526 and527, but only one of them may be provided. In FIG. 22B, because themagnetic flux intending to leak upward from the top face of the pole ofthe yoke 523 is introduced into the magnetic path by the magnet 528, themagnetic flux passing through the magnetic path space 525 is increased.As a result, the excitation unit 50 having the yoke-holding unit 52employing the modification 13 shown in FIG. 22A or 22B can obtain driveforce larger than that of the excitation unit 50 shown in FIGS. 5 and14, for example.

[Modification 14]

Whereas, in the embodiment described with reference to FIG. 13, in orderto determine the frequency characteristics H and L to be set in theequalizer unit 152, the signal generation unit 15 generates an impulsesignal and input the same to the excitation units 50H, 50L as the drivesignal, another construction may be employed as mentioned below. Namely,the drive signal output from the signal generation unit 15 to theexcitation units 50H, 50L is not limited to the impulse signal, but maybe another waveform signal such as time-stretched pulse (TSP) signal ora swept sine signal.

However, when a signal like the TSP signal which continues longer thanthe impulse signal is supplied to the excitation units 50H, 50L, to thesoundboard 7 currently vibrating in response to a preceding part of thesignal, excitation by a following part of the signal is added. In thiscase, it is recommended to remove an influence by the additionalexcitation onto the vibration waveform of the soundboard 7 bysubtracting waveforms indicated by the drive signal from voltagewaveforms obtained by measuring the vibration of the voice coil.

Alternatively, in order to determine the frequency characteristics H andL to be set in the equalizer unit 152, instead of excitation of thesoundboard 7 in response to the impulse signal from the excitation units50H, 50L, it may be configured such that a person in charge ofadjustment in a manufacturing process actually strike the soundboard 7at the connection positions H, L with a hammer or the like (a tool whichnever damages the soundboard 7 by striking) and then the frequencycharacteristic specifying unit 155 processes voltage valuescorresponding to resultant vibration of the soundboard 7.

[Modification 15]

Whereas, in the above-described preferred embodiment and modification,the piano is employed as an example of the keyboard instrument. However,the present invention may be applied to other keyboard instrument thanthe piano, such as a celesta having a metallic sound board as a soundingbody instead of the string, or a percussion instrument.

This application is based on, and claims priorities to, JP PA No.2011-200677 filed on 14 Sep. 2011, JP PA No. 2011-200678 filed on 14Sep. 2011, JP PA No. 2011-200679 filed on 14 Sep. 2011, JP PA No.2012-200456 filed on 12 Sep. 2012, JP PA No. 2012-200457 filed on 12Sep. 2012 and, JP PA No. 2012-200458 filed on 12 Sep. 2012. Thedisclosure of the priority applications, in its entirety, including thedrawings, claims, and the specification thereof, are incorporated hereinby reference.

What is claimed is:
 1. A keyboard instrument comprising: a plurality ofkeys; a plurality of sounding bodies each provided in correspondingrelation to each of the plurality of keys; a plurality of hammers eachresponsive to an operation of any one of the keys and adapted to strikethe sounding body corresponding to the operated key; a soundboardconfigured to be vibrated with vibration of the sounding body; anexcitation unit comprising a vibration member connected to a givenposition on the soundboard and adapted to vibrate the soundboard via thevibration member in response to a drive signal supplied thereto; aperformance information generation unit adapted to generate performanceinformation corresponding to an operation of the key; and a signalgeneration unit adapted to generate an audio waveform signal based onthe performance information, the generated audio waveform signal beingsupplied to the excitation unit as the drive signal to vibrate thevibration member, wherein the signal generation unit generates the audiowaveform signal having frequency characteristics which are adjusted inassociation with vibration characteristics of the soundboard at thegiven position where the vibration member is connected to.
 2. Thekeyboard instrument according to claim 1, wherein a plurality of theexcitation units are provided on different given positions of thesoundboard, wherein the signal generation unit generates a plurality ofthe audio waveform signals each having the frequency characteristicsunique to each excitation unit.
 3. The keyboard instrument according toclaim 1, wherein the signal generation unit generates the audio waveformsignal having the frequency characteristics for suppressing resonancecharacteristics of the soundboard at the given position where thecorresponding vibration member is connected to.
 4. The keyboardinstrument according to claim 1, wherein the signal generation unitgenerates the audio waveform signal having the frequency characteristicscorresponding to substantially inverse characteristics to the vibrationcharacteristics of the soundboard at the given position where thecorresponding vibration member is connected to.
 5. The keyboardinstrument according to claim 1, wherein a first bridge and a secondbridge are provided on the soundboard, and the excitation unit includesa first excitation unit connected to a position corresponding to thefirst bridge on the soundboard and a second excitation unit connected toa position corresponding to the second bridge on the soundboard.
 6. Thekeyboard instrument according to claim 1, further comprising: a stopperconfigured to be capable of for preventing the hammer from striking thesounding body; and a controlling unit adapted to control the stopper insuch a manner as to permit or not to permit the stopper to prevent thehammer from striking the sounding body when the soundboard is vibratedby the excitation unit.
 7. The keyboard instrument according to claim 1,wherein any one of a plurality of sound generation modes is selectable,and when a predetermined special sound generation mode is selected by auser from among the plurality of the sound generation modes, thesoundboard is vibrated by the excitation unit.
 8. The keyboardinstrument according to claim 1, wherein the excitation unit includes avoice coil adapted to be driven by the drive signal, and the keyboardinstrument further comprises a frequency characteristic setting unitadapted to, in order to previously set up the frequency characteristics,cause a vibration in the soundboard; measure a voltage induced in thevoice coil in response to the vibration caused in the soundboard;specify the vibration characteristics of the soundboard based on themeasured voltage; and set up the frequency characteristics of the audiowaveform signal to be generated by the signal generation unit based onthe specified vibration characteristics.